KR100293619B1 - Image-casting control method for image display device and image display device - Google Patents

Abstract

Disclosed is a video display device equipped with a fast-moving electron source. After the device is turned on, it is detected that sufficient deflection current is flowing from the horizontal / vertical deflection circuit to the deflection yoke so that the electron beam properly scans the screen, and then a drive signal is output from the RGB output circuit to each RGB electron source.

Description

Image casting control method and image display device for an image display device {IMAGE-CASTING CONTROL METHOD FOR IMAGE DISPLAY DEVICE AND IMAGE DISPLAY DEVICE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video casting control method of a cathode ray tube video display device for a television receiver or a data terminal device, and more particularly, to a video casting control method of a cathode ray tube video display device having a cold cathode.

The basic operation of a cathode ray tube involves the emission of light, that is, the excitation of fluorescent material on the screen by the electron beam using electron emission, focusing, acceleration, deflection from the electron source. The cathode ray tube of the prior art uses a hot electron source in an electron source using a phenomenon through hot electron emission.

This hot electron source, commonly used in cathode ray tubes, obtains hot electrons by using a heater to heat a cathode pallet consisting of oxidizing mixtures such as barium, calcium and strontium. The electron gun is constructed by combining these hot electron sources with a plurality of electrodes, and various functions such as focusing and accelerating the electron beam as well as controlling the amount of electron emission can be achieved by applying a predetermined voltage to each electrode.

When the power source is turned on to operate the hot electron source in a stationary state, it takes about 5 seconds to increase the temperature of the hot electron source from room temperature to a predetermined temperature (eg, about 750 ° C.) to enable electron emission.

On the other hand, when the operating hot electron source is stopped, it takes a few seconds before the temperature drops (about 500 ° C) to the point where electron emission ends even when the power of the heater is cut off. During this interval, hot electrons are emitted from the cold cathode. And the electron beam is emitted towards the screen.

In a display device using a cathode ray tube, a large capacity smoothing capacitor is used as a high voltage power supply that applies a positive high voltage on a screen to stabilize a high DC voltage when the power supply is turned off. As a result, even when the power supply is cut off, the high voltage output is not immediately interrupted, but gradually falls. In comparison, horizontal and vertical deflection circuits that do not use hot electrons quickly drop high voltage outputs, resulting in a state in which the electron beam is not fully deflected and continues to emit for a time interval focused on the center of the fluorescent screen. In this state, the result is a problem of residual spots that can result in "sticking" or burning in the center of the phosphor screen. Several image output circuit control methods, commonly referred to as "spot killer", have been disclosed as a means to prevent this phenomenon after the emission of the electron beam has reached a steady state.

As shown in Fig. 1, Japanese Patent Laid-Open No. 231567/91 discloses a method of preventing residual spots by charging the capacitor 24 after the power is turned on and reaching a steady state, when the power is turned off. The voltage drop at the + B terminal is detected so that the spot killer circuit 22 is activated, and the voltage of the charged capacitor 24 is used to change the bias of the image output circuit 23 in the direction in which the beam current flows, The high voltage charged in the cathode ray tube 21 is discharged before the horizontal and vertical deflection circuits stop operation.

Japanese Patent Laid-Open No. 245178/88 discloses a method for the case where the circuit system as shown in FIG. 2 is digitized. When the synchronous deflection circuit 39 is digitized, when the power supply is turned off, a voltage drop is detected, and the system reset circuit 32 is operated so that the synchronous deflection circuit 39 is momentarily stopped, thereby horizontally and vertically. Deflection is no longer performed. To prevent this from happening, the system reset signal turns on the on-screen blanking transistor 33, which causes the image output transistors 35, 36, and 37 of the image output circuit 34 to turn off momentarily. The cathode ray tube (not shown) enters a blanking state where the bias of the cathode is blocked and electron emission is stopped. Thus, the electron beam can be prevented from entering the static spot state. On-screen blanking used in this case is a function used to blank the background part of the characters displayed on the screen.

A cathode ray tube using a cold cathode, such as a field emission cold cathode, which is a quick-acting electron source as an electron source, does not require heating of a cathode ray by a heater required for a hot cathode. The principle of electron emission of field emission cold cathodes is the emission of electrons from solid to vacuum generated by the quantum mechanical tunnel effect when a strong electric field of 10 ⁷ V / cm or more is applied to the solid surface.

3 shows an example of the configuration of the field emission cold cathode. A high electric field can be obtained by the voltage applied between the sharp needle-type emitter electrode 15 having a tip radius of about 100 nm and the gate electrode 14 arranged approximately 0.5 to 1 탆 away from the emitter. Therefore, electric field concentration occurs at the tip of the emitter electrode 15. Multiple emitter-gate structures of this type formed on the substrate 12 and connected in parallel can be used to lower the applied voltage to obtain a predetermined current.

The sharpness grade of the tip of the emitter electrode 15 and the insulating properties between the emitter electrode 15 and the gate electrode 14 are important conditions for maintaining the electron emission characteristics of the field emission cold cathode.

As mentioned above, the size of each emitter and gate is extremely small, and a large number of components can be integrated in a small area. As shown in FIG. 4, an example of electron emission characteristics with respect to an applied voltage is shown in which electron emission starts at approximately 30V and rises rapidly.

However, the above-described prior art has the following problems. First, when the power of a display device using a cathode ray tube using a fast-moving electron source, such as a field emission cold cathode, is turned on, the electron beam is emitted only to the center of the screen, thereby causing burning of the fluorescent screen. As a result, electron emission from the field emission cold cathode immediately begins when a voltage satisfying the predetermined electron emission condition is applied. When the device is turned on, electron beams are emitted to the center of the screen without experiencing deflection since the horizontal / vertical deflection circuits start emitting electrons before they sufficiently rise.

The second problem is the deterioration of the insulating properties caused by the damage of the constituent elements caused by the sputtering caused by the impact of the cations and the recombination of the sputtered fine particles. The electron beam ionizes the remaining gas molecules or gas molecules generated by the irradiation of the screen in the cathode ray tube, and the cations generated thereby are accelerated in the direction opposite to the electron beam. When the electron beam is deflected in a fixed state, the paths of electrons and cations are different depending on the mass difference, so that the cations do not reach the electron source. However, if the electron beam goes straight without deflection, the cations will impact the electron source. As shown in FIG. 3, since the field emission cold cathode is subjected to voltage input to the microstructure, the field emission cold cathode is extremely sensitive to the impact of the cations.

It is an object of the present invention to provide a method and apparatus for preventing residual spots when power is turned on in an image display apparatus equipped with a fast-type electron source.

Another object of the present invention is to provide a method and apparatus for improving reliability and lifespan of an image display apparatus by preventing a concentrated cation impact of a cathode in a device equipped with a fast-type electron source.

The image casting control method of the image display apparatus of the present invention is to delay the start of operation of the electron source until the electron beam deflection system reaches a normal operating state when the power is turned on.

According to the present invention, in an image display apparatus equipped with a fast-moving electron source such as a field emission cold cathode, electron emission does not start even after the power of the apparatus is turned on, even after the horizontal / vertical deflection output circuit is sufficiently raised, Accordingly, burning of the fluorescent screen can be prevented when the power is turned on.

According to the present invention, despite the ionization of gas molecules and the generation of cations in the cathode ray tube by the electron beam, most of the cations are because the electron beam is deflected and the electrons and cations have different paths due to their mass differences. The electron source is not reached, thereby suppressing not only the deterioration of the insulating property due to the recombination of the sputter particles, but also the damage of the constituent elements caused by the sputtering due to the impact by the cations.

In addition, the video display device according to the present invention,

A deflection current detection circuit for driving the RGB output circuit or the RGB preamplifier only when a deflection current sufficient for the electron beam to properly scan the screen flows from the horizontal / vertical deflection output circuit to the deflection yoke; or

After the main power of the device is turned on, when driving the horizontal / vertical deflection output circuit and supplying deflection current to the deflection yoke, and when there is enough deflection current for the electron beam to properly scan the screen, the RGB output circuit or RGB preamplifier It includes a system control circuit for driving the.

The above and other objects, features and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings, in which embodiments of the present invention are shown.

1 is a block diagram showing a spot killer circuit of the prior art;

2 is a block diagram showing main elements of a television receiver of the prior art;

3 is a partial perspective view showing the structure of the field emission cold cathode device;

4 shows an example of field emission cold cathode current-voltage characteristics;

5 is a block diagram showing main elements of an image display apparatus according to a first embodiment of the present invention;

6 is a block diagram showing main elements of an image display apparatus according to a second embodiment of the present invention;

<Explanation of symbols for the main parts of the drawings>

1: cathode ray tube

2: deflection yoke

3: screen

4: RGB output circuit

5: horizontal / vertical deflection output circuit

6: grid power

7: anode power

8: deflection current detection circuit

10: RGB preamplifier

11: sync signal processing circuit

Referring to Fig. 5, the image display apparatus of the first embodiment of the present invention comprises: a cathode ray tube 1 having a deflection yoke 2 and a screen 3, an RGB output circuit 4, and a horizontal / vertical deflection output circuit. (5), grid power supply 6, anode power supply 7, deflection current detection circuit 8, RGB preamplifier 10, sync signal processing circuit 11, and other circuits not shown.

First, the basic configuration and operation of the image display apparatus using the cathode ray tube 1 equipped with the field emission cold cathode will be described. Electron emission is caused by application of a drive signal corresponding to the image input signal from the RGB output circuit 4 to the respective RGB electron sources. In the case of driving a cathode ray tube equipped with field emission cold cathodes having the current-voltage characteristics shown in FIG. 4, if the maximum current is, for example, 1 mA, it is 1 from the gate voltage of 35 V to start electron emission. An amplitude modulated voltage up to 55V capable of obtaining an emission current of is output from the RGB output circuit 4; Electron emission occurs by applying this voltage between each of the emitter electrodes and the gate electrodes of each of the RGB field emission cold cathodes. The emitted electrons are concentrated and accelerated by the voltage applied by the grid power supply 6 to form an electron beam with a grid (not shown) arranged in front of the electron source. The electron beam is horizontal by a magnetic field generated by supplying horizontal and vertical deflection currents corresponding to the image input signal from the respective horizontal / vertical deflection output circuits 5 to the deflection yoke 2 disposed outside the cathode ray tube 1. And deflected in the vertical direction, the electron beam scans the screen 3 to which the fluorescent material is applied. A voltage of about 20 KV is applied to the screen 3 by the anode power supply 7, and the fluorescent material excited by the electron beam emits light to display an image. Here, the RGB output circuit 4 does not unconditionally output drive signals. Rather, the apparatus is configured such that the deflection current is detected by the deflection current detection circuit 8, and the RGB output circuit 4 has a deflection current sufficient for the electron beam to scan the screen 3 in the horizontal / vertical deflection output circuit. It is driven only when flowing from the deflection yoke 2 to the deflection yoke 2. For example, the deflection current detection circuit 8 integrates the deflection waveform to detect the integral value level.

Next, an operation of turning on the main power of the video display device until the steady state is reached will be described. When the main power of the apparatus is turned on, the respective components are powered up and the circuits start to operate. However, when the deflection current detection circuit 8 does not control the RGB output circuit 4, the field emission cold cathode immediately starts to emit electrons upon voltage input. Conversely, the rise of the horizontal / vertical deflection output circuit 5, depending on the inductance of the coil, until a sufficient normal magnetic field distribution is reached, requires about one or two second intervals. For one or two seconds, the electron beam does not experience deflection or suffers from insufficient deflection, so that it is irradiated and concentrated at one point or micro area of the center of the screen 3, causing damage to the fluorescent layer. This problem does not occur when using a hot cathode that requires time for temperature rise.

When the deflection current detection circuit 8 performs control of the RGB output circuit 4, the drive signal is not output to the field emission cold cathode until the horizontal / vertical deflection output circuit 5 is sufficiently raised, so that the electron beam It is not concentrated in any particular area of this screen, and damage to the fluorescent layer can be prevented.

In addition, residual gas molecules are present in the cathode ray tube 1, and the gas absorbed on the screen surface is also removed by irradiation of the screen 3 by the electron beam. Irradiation of these gas molecules by the electron beam causes ionization of the gas molecules and generation of cations. In the state where the electron beam is not deflected, the electron beam follows a straight path, thus reaching and impacting the field emission cold cathode. The cations that impact the field emission cold cathode cause sputtering at the tip of the emitter electrodes, resulting in blunt tips and deterioration of electron emission characteristics. Recombination of the sputtered materials also creates a leakage path between the emitter electrodes and the gate electrodes, which lowers the insulating properties and shortens the life of the device. However, in the normal operating state in which the electron beam is deflected, electrons and cations move in different paths by their mass difference, virtually the cations do not reach the electron source.

According to the determination criteria used in the deflection current detection circuit 8 of this embodiment for determining whether to drive the RGB output circuit, it is not necessary that the amplitude of the deflection current reaches 100% of the deflection current in the steady state. Sufficient effects can be achieved with lower amplitudes of 70 to 80% or more.

Although the deflection current detection circuit 8 of this embodiment is configured to control the RGB output circuit 4, an equivalent effect can be obtained by the configuration in which the deflection current detection circuit 8 controls the RGB preamplifier 10. FIG.

This embodiment can be applied to various forms of field emission cold cathodes without being limited to any particular form. For example, in a field emission cold cathode, emitter electrodes 15 may be formed of silicon substrates of known forms, including " spin-shaped " as shown in FIG. 3, formed by deposition using a process such as vacuum deposition. It may take a variety of forms, such as a form commonly referred to as "vertical" in which protruding electrodes are formed by etching, or a form commonly referred to as "horizontal" formed by patterning a film by photolithography and etching.

Referring to FIG. 6, the image display apparatus according to the second embodiment of the present invention is the same as the fifth embodiment shown in FIG. 5 except for the system control circuit 9 that replaces the deflection current detection circuit 8. .

Most image display devices for workstations or personal computers perform the display by automatically following various forms of image signals (signals with different combinations of horizontal / vertical sync frequencies). This type of video display device incorporates a microcomputer in the device to perform signal processing or system control. In this embodiment, the RGB output circuit 4, the grid power supply 6, the horizontal / vertical deflection output circuit 5 and the anode power supply 7 required for driving the cathode ray tube are in the same manner as in the first embodiment. Connected. However, the operation and output signals of each of these drive circuits can be controlled by signals from the system control circuit 9 including the microcomputer.

Next, the operation from the time when the main power of the image display apparatus is turned on until reaching the stop operation state will be described. When the main power of the device is turned on, power is applied to each component starting with the system control circuit 9, but the respective drive circuits at this point are in a standby state so that the drive signals are output to the cathode ray tube 1 It doesn't work. Next, a deflection current is supplied from the horizontal / vertical deflection output circuit 5 to the deflection yoke 2 in accordance with the signal from the system control circuit 9. For a time difference of a few seconds (e.g., 2 to 3 seconds), the RGB output circuit 4 starts to output a drive signal in accordance with the signal from the system control circuit 9, so that electron emission and image display start. .

Therefore, since the electron emission starts at a certain time difference after the deflection current starts to flow, it is possible to prevent damage in the fluorescent layer as in the case of the first embodiment, and to suppress the adverse effect on the electron source caused by the cation impact. Can be.

In the first and second embodiments, the image display apparatus equipped with the field emission cold cathode as the fast-moving electron source has been described, but the MIM (metal-insulator-metal) of surface conduction type, PN junction type, or photoelectron emission type is described. Equivalent effect can be obtained in an image display apparatus equipped with tunnel-type cold cathodes, such as a) structure or a MIS (metal-insulator-semiconductor) structure.

Also, in the first and second embodiments, apparatuses using cathode ray tubes as image display apparatuses have been described, but the present invention is applied to other display apparatuses in which an electron beam is deflected and scanned, such as an electrostatically deflected surface display. It is possible to obtain an equivalent effect by using this.

While the preferred embodiments of the present invention have been described using specific forms for purposes of illustration only, it will be understood that they may be changed and modified without departing from the spirit or scope of the following claims.

The present invention described above has the following effects.

(1) After the power supply of the device is turned on, since the vertical deflection circuit is sufficiently raised, electron emission is started. Therefore, the fluorescent surface is turned on while the power supply of the video display device equipped with the fast-moving electron source such as a field emission cold cathode is turned on. Can prevent damage.

(2) The electron beam ionizes the gas molecules in the cathode ray tube to generate cations, and when the electron beam is deflected, the paths are different from each other by the mass difference of the electrons and cations, so that the cations hardly reach the electron source. By the sputtering of the cation, deterioration of the insulating property caused by the recombination of the sputtered fine particles of the electronic structure can be suppressed.

Claims (8)

In the image casting control method of a video display device equipped with a fast-moving electron source, Turning on main power of the image display apparatus; Detecting whether the electron beam deflection system has reached a normal operating state; And Supplying a driving signal corresponding to an image input signal to the electron source when it is detected that the electron beam deflection system has reached a stationary operation state Image casting control method comprising a. 2. The method of claim 1, wherein the detection of whether the electron beam deflection system has reached a stationary operating state is performed by detecting whether sufficient deflection current flows into the deflection yoke to properly scan the screen by the electron beam. Image casting control method. In a video display device equipped with a fast electron source, An RGB output circuit for outputting device signals corresponding to the image input signals to respective RGB electron sources; An RGB preamplifier for amplifying RGB image input signals and outputting the amplified RGB image input signals to the RGB output circuit; Horizontal / vertical deflection output circuit; And A deflection current detection circuit that drives the RGB output circuit or the RGB preamplifier when it detects that sufficient deflection current flows from the horizontal / vertical deflection output circuit to the deflection yoke so that an electron beam properly scans the screen. Image display apparatus comprising a. The image display apparatus of claim 3, wherein the rapid electron source is a cold cathode. The image display apparatus of claim 3, wherein the cold cathode is any one of a field emission type, a tunnel type, a surface conduction type, a PN junction type, and a light pump type cold cathode. In a video display device equipped with a fast electron source, An RGB output circuit for outputting driving signals corresponding to the image input signals as RGB electron sources; An RGB preamplifier for amplifying RGB image input signals and outputting the amplified RGB image input signals to the RGB output circuit; Horizontal / vertical deflection output circuit; And After the main power of the device is turned on, when driving the horizontal / vertical deflection output circuit and supplying deflection current to the deflection yoke, and when sufficient deflection current flows for the electron beam to properly scan the screen, the RGB output circuit or the RGB System control circuit driving preamplifier Image display apparatus comprising a. The image display apparatus of claim 6, wherein the rapid electron source is a cold cathode. The image display apparatus of claim 6, wherein the cold cathode is any one of a field emission type, a tunnel type, a surface conduction type, a PN junction type, and a light pump type cold cathode.

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